Used MT, bought on auction.
Turned ON ok, default login OK, default config applied successfully.
After upgrade stopped responding.

I've tried netinstall (on 4 different computers with 3 different Windows versions) without success.
Netinstall wasn't able to see the router.

I've tried wireshark to sniff traffic when router tries to find netinstall.
Wireshark recorded only packets originating from my network card.
(no packet with eth.src different from NIC MAC).

Is there anything else that I can do ?

You could try the Linux version of netinstall.

Disable all network interfaces on your computer except for wired connection.

Set fixed IP on network interface as instructed.
Use switch between PC and router when doing netinstall, so network interface doesn't go up/down all the time.